WASHINGTON (CNN) -- Congress Tuesday passed a 15-day extension of a temporary surveillance law set to expire later this week, buying itself more time to come up with a permanent fix for the measure.

The House and Senate passed the extension of the Protect America Act -- the law that was hastily passed in August when the Bush administration warned of gaps in its ability to monitor suspected terrorists.

President Bush is expected to sign the extension.

But prospects for a permanent law seem as daunting now as they did in August, when Congress agreed to the temporary measure so lawmakers could try to reconcile their differences.

While the House has already passed a version of the bill -- which does not include retroactive immunity for telecommunication companies that helped government wiretapping efforts without a court order -- Democratic and Republican senators are at odds.

Republicans want a vote on the Bush administration-supported bill, which enhances the government's surveillance capabilities and provides immunity for the telecommunication companies.

Democrats want to debate and vote on a number of amendments, including one that would strip the controversial liability protection out of the bill.

The House version also also gives the Foreign Intelligence Surveillance Act court more oversight over the program.

Differences between the House and Senate bills would have to be reconciled before a bill could be sent to the White House for the president's signature.

Bush has threatened a veto if the bill does not include the immunity clause.

On Tuesday, the Senate fell 12 votes short of the 60 needed to cut off debate and proceed toward a vote on the bill. By a similar vote, Democrats failed to extend the Protect America Act for 30 days. The act was set to expire Friday.

Critics of the law say it allows the government to spy on Americans without a court order.E-mail to a friend